1. Field of the Invention
The present invention relates to a radio communication apparatus and a radio communication method.
2. Related Art
A receiving unit of a conventional wireless LAN apparatus uses an error correction code and an error detection code to control frame errors. An error correction code adds appropriate redundancy to information (a message) to be transmitted to a receiving end. Errors that occur in a communication channel are corrected at the receiving end on the basis of the error correction code. An error detection code adds appropriate redundancy to a message. Errors that occur in a communication channel are detected at a receiving end on the basis of the error detection code.
A receiving unit of a conventional wireless LAN apparatus includes an antenna section, a demodulating section, an error correcting section, an error detecting section, and a retransmission control section.
Data received at the antenna section is decoded by the demodulating section and error correction is performed by the error correcting section on the basis of an error correction code added at a transmitting device. The error detecting section performs error detection on the basis of the error detection code added at the transmitting device. If not all errors can be corrected at the error correcting section, errors are detected at the error detecting section. In that case, the retransmission control section performs retransmission control. Some method is used to cause the other end of communication to retransmit the data.
For example, a wireless LAN apparatus requests the transmitting end to retransmit a frame in which an error has occurred, by not returning an Ack (Acknowledgement) frame to the transmitting end. Conversely, if the apparatus properly receives a frame transmitted to it, it returns an Ack frame to the transmitting end.
Consider a situation in which a first terminal transmits a data frame to a second terminal and the second terminal that has received the data frame returns an Ack frame to the first terminal.
Suppose the Ack frame transmitted from the second terminal to the first terminal includes an error even though the second terminal has received correct data frame without errors from the first terminal. If an Ack frame cannot be correctly received, the effect is as if no Ack frame were transmitted. In this case, the data frame will be retransmitted in accordance with the mechanism of retransmission control.
An Ack frame is typically a short frame that only includes minimum information such as a frame type and a destination address. Therefore the most part of the information in the frame is known or can be estimated before its reception. In terms of the communication quality and power consumption of radio communication systems, it is not beneficial to determine only on the basis of the mechanism of error correction and error detection that a frame is an error frame, and to request retransmission of the frame.